Module adc 

Analog to Digital Converter (ADC)

Overview

The ADC is integrated on the chip, and is capable of measuring analog signals from specific analog I/O pins. One or more ADC units are available, depending on the device being used.

Configuration

The ADC can be configured to measure analog signals from specific pins. The configuration includes the resolution of the ADC, the attenuation of the input signal, and the pins to be measured.

Some targets also support ADC calibration via different schemes like basic calibration, curve fitting or linear interpolation. The calibration schemes can be used to improve the accuracy of the ADC readings.

Examples

Read an analog signal from a pin

let mut adc1_config = AdcConfig::new();
let mut pin = adc1_config.enable_pin(peripherals.GPIO0, Attenuation::_11dB);
let mut adc1 = Adc::new(peripherals.ADC1, adc1_config);

let mut delay = Delay::new();

loop {
    let pin_value = nb::block!(adc1.read_oneshot(&mut pin))?;

    delay.delay_millis(1500);
}

Implementation State

• ADC calibration is not implemented for all targets.
• The ESP32-S31 has no calibration scheme. ESP-IDF does not define the calibration eFuses or the curve fitting coefficients for this chip yet.
• The ESP32-S31 SAR ADC has one attenuation setting, so the attenuation given to AdcConfig::enable_pin has no effect.
• The ESP32-S31 SAR is differential and its result is the weighted sum of 17 redundant comparator bits. Readings run from 0 to FULL_SCALE (4393), and an input tied to ground reads about ZERO_DIFF_CODE (2198), so a single-ended measurement only uses the codes above that point.

Structs

Adcunstable

Analog-to-Digital Converter peripheral driver.

AdcCalBasicunstable

Basic ADC calibration scheme

AdcCalCurveunstable

Curve fitting ADC calibration scheme

AdcCalLineunstable

Line fitting ADC calibration scheme

AdcConfig

Configuration for the ADC.

AdcPin

An I/O pin which can be read using the ADC.

Enums

AdcCalSource

Calibration source of the ADC.

Attenuation

The approximate attenuation of the ADC pin.

Traits

AdcCalScheme

A trait abstracting over calibration methods.

AdcChannel

A helper trait to get the ADC channel of a compatible GPIO pin.

AdcHasCurveCalunstable

Marker trait for ADC which support curve fitting

AdcHasLineCalunstable

Marker trait for ADC units which support line fitting.

Instanceunstable

Enable asynchronous access.